Glutamic acid is an excitatory neurotransmitter most abundantly present in the central nervous system of mammals. Glutamic acid plays an important role in the cognition, mood and control of motor function, and these processes become unstable in mental diseases and neuropathy. Glutamic acid receptors are classified into ion channel-type receptor and G protein conjugated-type receptor, and the ion channel-type receptor is further classified into α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor, N-methyl-D-aspartic acid (NMDA) receptor and kainic acid (KA) receptor. (non-patent document 1)
AMPA receptor is one kind of receptor for excitatory neurotransmitter glutamic acid, and was named based on selective activation of the receptor by AMPA. AMPA receptor consists of 4 subunits (GluR1, GluR2, GluR3, GluR4). It includes homomeric receptor constituted, with the same kind of subunits and heteromeric receptor constituted with heterogeneous subunits. It has been reported that the physiological property of AMPA receptor varies depending on the subunits constituting the receptor. (non-patent document 1, 2, 3)
Activation of AMPA receptor is known to cause various intracerebral actions (neural activation, enhancement of neural plasticity, enhancement of neurogenesis, enhancement of BDNF production and the like) (non-patent documents 4, 5, 6, 7). Therefore, a compound having an AMPA receptor function enhancing action is expected to be useful as a drug for the prophylaxis or treatment of mental diseases, neurodegenerative disease, memory disorders, sleep disorder and the like. (non-patent documents 8, 9)
As a compound having an AMPA receptor function enhancing action, patent document 1 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 2 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 3 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 4 discloses a sulfonamide derivative having an AMPA receptor function enhancing action; which is represented by the formula

Patent document 5 discloses an indazole derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 6 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 7 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 8 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 9 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 10 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 11 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 12 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 13 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

Patent document 14 discloses a sulfonamide derivative having an AMPA receptor function enhancing-action, which is represented by the formula

Patent document 15 discloses a sulfonamide derivative having an AMPA receptor function enhancing action, which is represented by the formula

However, there is still a demand for the development of a sulfonamide derivative having an AMPA receptor function enhancing action.